1. Field of the Invention
Balloon angioplasty was introduced to open vessels, particularly blood vessels which have narrowed as a result of plaque progression or a heart attack. In successful cases, the blood vessel remained open and/or exhibited positive remodeling over time and/or exhibited vasodilation ability mimicking to a degree the natural vessel ability. In other cases, however, the blood vessel would re-occlude within few days or within months due to various causes such as recoil of the vessel, thrombus formation, or other type of plaque morphology progression.
Metallic stents were developed to provide a structure, often referred to as a scaffold, with sufficient radial strength (crush resistance) to address recoil and hold the vessel open over time. Stents were formed from wire(s), coils, braids, a sheet, and/or tubular bodies. Balloon expandable stents formed from patterned non-degradable metallic tubes, wires, or sheet, are now most commonly used as they display desirable structural characteristics such as limited inward recoil, high strength (crush resistance or crush force), and limited axial shortening upon expansion, when compared to some earlier coiled or braided stents.
Despite their success and widespread adoption, metallic stents such as stainless steel alloys, Platinum iridium alloys, and cobalt chrome alloy stents, suffer from certain shortcomings, such as they jail the lumen or vessel, they do not further expand (after inward recoil) after implantation under physiologic conditions, preventing the lumen or vessel from further expanding which in turn inhibits positive remodeling, and/or such stent inhibits vasodilation or vasomotion of the treated vessel stent segment which is important to healing of the vessel or the normal functioning of the vessel. This phenomenon is commonly referred to as “jailing” or “caging” the vessel. High radial strength is important to support a body lumen upon implantation and/or to maintaining it open upon implantation of the stent and/or high strength is important in preventing the lumen from getting smaller after implantation. In some cases where shape memory self expandable alloys stents are used such stents typically do not exhibit high radial strength (high crush force resistance) like the metallic stents due to the material properties (and as a result the lumen in some cases become smaller after implantation of such stents due to excessive inward recoil due to lumen inward force on the stent and/or due to the lower radial strength of these stents, making such stent less likely to further expand after implantation in a lumen or diseased lumen segment, and/or such stents are less likely to exhibit vaso-dilatation or vaso-motion of the stented segment. In some cases shape memory stents penetrate the lumen wall moving towards the adventitia causing irritation, inflammation of the vessel or lumen, sometimes resulting in unwanted negative clinical events and/or re-occlusion of the body lumen or vessel. Also, the stent is typically maintained in the crimped configuration using a constraint upon delivery into the vessel or lumen which makes the profile of the stent system large and less deliverable. Stents of this type are usually pre-programmed to expand to a certain diameter/configuration which makes sizing limited to such pre-programmed diameter/configuration and less likely to expand or maintain an expanded diameter beyond such pre-programmed diameter, which makes stent sizing more difficult, and/or such stents do not expand further beyond such pre-program diameter/configuration after deployment, to name a few.
To address some of these shortcomings, biodegradable stents or scaffolds made from metallic or polymeric materials were developed. By allowing the stent to degrade or resorb, the jailing or caging effect would diminish or decrease over time and the scaffold would finally disappear over time. Present biodegradable stents, however, and in particular polymeric biodegradable stents and corrodible metallic stents, have their own shortcomings, including stent fractures, and/or limited ability to over-expand the stent above a nominal expanded diameter, and/or have excessive or high initial inward recoil, and/or have additional inward recoil after implantation and after the initial inward recoil. In some cases they may have insufficient strength to accommodate various lesion types after deployment, and/or limited ability to maintain a lumen or vessel open after deployment. Biodegradable stents typically have lower radial strength (crush resistance/strength) than balloon expandable metallic non-degradable stents, typically are bulky thick strut stents in order to address some of the mechanical shortcomings such as suboptimal crush strength, or having thick struts, which can cause negative clinical events, may cause excessive inflammation (due at least in part to the degradation of the material and the quantity of the degradation material), and/or cause excessive hyperplasia such as neo-intimal hyperplasia (due to at least in part to the degradation of the material and the quantity of the degradation material), to name a few problems.
Attempts have also been made to make scaffolds from a combination of polymeric and metallic materials. However, such designs have displayed their own shortcomings. Such combination designs can lack sufficient initial crush resistance to effectively open a lumen, or maintain it open, after implantation of the stent, or such designs do not uncage the stent, or do not uncage the stent along the entire stent segment, or do not uncage the vessel, or do not further expand the stent under physiologic conditions, or do not further expand the stent and/or allow it to contract using or after use of vaso-dilators and/or vaso-constrictors after implantation. Alternatively, some other such designs will not be able to further expand to a larger configuration (after inward recoil if any) after implantation. Still other designs have so many separate metallic or other non-degradable pieces that they risk releasing the small pieces into the blood stream potentially causing a clinical event. One or more needs as described above in the following exemplary issues remain unmet by present non-degradable stents: having a stent with low inward recoil, and/or having a stent with low initial inward recoil after expansion while the diameter of the stent is substantially maintained after implantation and after the initial inward recoil, and/or having a non-degradable stent configured to be able to further expand (after inward recoil if any) after deployment under physiologic condition, and/or having a stent able to expand or further expand (after inward recoil if any) after deployment without a pre-programmed temperature trigger setting or without a pre-programmed expanded diameter/configuration setting, and/or having a stent able to expand or further expand (after inward recoil if any) without a programmed temperature, and/or having a stent able to further expand (after inward recoil if any) after deployment under physiologic condition without penetrating or without substantially penetrating the vessel or lumen wall into the advantitia, and/or having a stent that does not cause excessive inflammation, and/or having a stent that does not penetrate the lumen or vessel wall after implantation into the advantitia, and/or having a stents that expands further following any inward recoil, after deployment (implantation) further expanding the lumen or vessel diameter, and/or having a stent maintained or substantially maintained in the crimped configuration upon delivery into the vessel or lumen without a constraint and which further expands after any inward recoil to a larger configuration after deployment, and/or having a stent that can be deployed to a wide range of diameters and still uncages the vessel or lumen after deployment, and/or having a stent that can be deployed to a wide range of diameters and still further expand after any inward recoil to a larger configuration after implantation, and/or having a stent able to further expand after any inward recoil beyond the pre-programmed expanded diameter/configuration after implantation, and/or having a stent that exhibit vaso-motion, vaso-dilation, or vaso-constriction, after implantation, and/or having a stent that has sufficient strength after deployment to support a body lumen, has low inward recoil, and where the stent exhibits radial strain of 1% or larger than 1% after deployment, and/or having a non-degradable stent having an initial compliance upon expansion from a crimped configuration to an expanded configuration, wherein the initial compliance increases after implantation, and/or having a non-degradable stent having an initial radial strength (crush resistance) upon expansion from a crimped configuration to an expanded configuration, wherein the initial radial strength decreases after implantation, and/or having a balloon expandable non-degradable stent capable of expanding from a crimped configuration to an expanded configuration, where the expanded configuration comprises diameters ranging from 2.0 mm to 4.0 mm, and wherein the stent exhibits initial inward recoil after an initial expansion, and said stent after initial recoil has an initial diameter, said stent maintains said initial diameter (or configuration) after said initial inward recoil, and wherein the stent responds to a vaso-dilator after implantation sufficient to expand the stented segment to a second diameter wherein the second diameter (or configuration) is larger than the initial diameter.
A particular concern in vascular and other body lumens after implementation of the stent or other prosthesis is the loss of vessel or lumen remodeling or enlargement, or the loss of vessel or compliance or contractility, referred to above as “caging” or “jailing” of the blood vessel or body lumen. Vessel compliance is necessary for the vessel or body lumen under physiologic conditions such as responding to changes in the internal pressure, external pressure, muscle contraction, muscle relaxation, chemical change, and the like. Such changes can result from many sources, such as the presence of natural, or artificial substances, which can relax or contract the body lumen and/or muscles such as smooth muscle cells, for example within the walls of the body lumen. The implantation of a stent in a blood vessel or body lumen will necessarily contribute to a reduction in the overall or “composite” compliance of the body lumen and the stent. Each of the body lumen's natural compliance and the stent's additional compliance will contribute to a total or overall “composite” compliance which will necessarily be less than that of the body lumen had the stent not been implanted. Thus, it is desirable for a stent implanted in body lumen, particularly implanted in a blood vessel, to minimize the reduction of body lumen compliance which naturally occurs as a result of the implantation of the stent. While a reduction of the compliance may be acceptable for a period of time immediately following implantation, particularly during that period (such as upon implantation or the initial period after implantation) when high radial strength is desired to maintain patency of the vessel (or body lumen) and prevent further inward recoil after implantation. Such strength is less necessary or not necessary after the initial period when healing of the vessel has occurred and eventually the strength of the stent becomes unnecessary or less important. During such healing phase or after such healing phase, it is highly desirable that the compliance of the vessel returned to levels at, or approaching, or closer to the natural compliance of the lumen in the absence of the implanted stent. Thus, it is an object of the present invention to provide stents, stent scaffolds, and other luminal prostheses which, after implantation, display a compliance which increases over time, in response to the vascular or other luminal environment, so that the total or composite compliance of the stents scaffold and the body lumen increase to levels which are closer or approach that of the body lumen in the absence of the stent scaffold.
Loss of compliance is also a problem for valves, rings, and other appliances implanted in heart valve annuluses. While valve scaffolds may not always need a high radial strength, particularly after an initial period of implantation, it is beneficial that they be sufficiently compliant to be able to conform to the annulus as the annulus deforms during the normal systoloic-asystolic cycle, or it deforms to conform to the deformed annulus due to disease progression thus maintaining the integrity of the valve function, or it dilates to conform to the annulus dilation due to physiologic conditions or progression of disease, while maintaining the integrity of valve function.
What is needed are implants, stents, stent scaffolds, vascular prostheses, ecto-prosthesis, and/or other luminal prostheses that addresses at least some of these shortcomings as well as others described herein.
2. Listing of Background Art
Relevant background patents and applications include: U.S. Pat. Nos. 7,011,678; 5,922,020; US2003/0153971; U.S. Pat. No. 9,056,157; US2005/0222671; U.S. Pat. Nos. 9,265,866; 7,169,173; 8,435,281; US2003/0195609; U.S. Pat. Nos. 7,402,168; 7,829,273; 5,695,516; 6,540,777; 8,652,192; 8,128,679; 8,070,794; 6,599,314; 8,961,585; 7,455,687; 7,645,409; 8,202,313; EP2229919; U.S. Pat. Nos. 6,251,134; 6,409,754; 5,766,237; 5,957,975; 5,306,286; 5,961,545; 8,052,743; 9,180,005; 9,192,471; US2008/177373; and US2005/283229.